“With a turnout like this, I’m beginning to feel we might win tomorrow,” an upbeat Romney told a crowd of several hundred at a stop in Dunedin on Monday as he and Gingrich zipped across the state making their final appeals.

Gingrich, in turn, acknowledged that his momentum had been checked but promised not to back down. He characterized Romney as an imposter, and his team started to plot a strategy for upcoming contests.

“He can bury me for a very short amount of time with four or five or six times as much money,” Gingrich said in a television interview. “In the long run, the Republican Party is not going to nominate … a liberal Republican.”

GOP officials in Florida were anticipating a big turnout, more than 2 million voters, up from a record 1.9 million in the Republican primary in 2008. More than 605,000 Floridians had already voted as of Monday, either by visiting early voting stations or by mailing in absentee ballots, ahead of the total combined early vote in the GOP primary four years ago.

In the span of a volatile week, the tables have turned in this potentially pivotal primary state.

Gingrich rode a triumphant wave into Florida after a South Carolina victory nine days ago. But since then, Romney and his allies have pummeled the former House speaker on TV and on the campaign trail. Romney turned in two strong debate performances, while Gingrich faltered. Now opinion polls show the former Massachusetts governor with a comfortable lead here.

Romney and Gingrich have been the only two candidates to compete in Florida in earnest. Neither former Penn- sylvania Sen. Rick Santorum nor Texas Rep. Ron Paul campaigned much in the state, and they were elsewhere on Monday.

A win by Romney would again reset the 2012 GOP race, seen early this month as his to lose, then thrown into doubt by Gingrich’s come-from-behind win in South Carolina.